Interference of autoionising transitions in separate atoms: a theoretical analysis applied to electron distributions from He++He collisions

Sharp interference structures in the angular distributions of autoionisation electrons from He + +He collisions are measured and interpreted quantitatively. A comprehensive derivation of a semiclassical theory is given which describes energy spectra and angular distributions of autoionisation electrons from collisionally excited atoms. The description includes post-collision interaction. Special emphasis is given to those cases where electron emission from target and projectile cannot be distinguished from each other, giving rise to interference effects. The experimentally observed interferences are reproduced without an adjustment of the free fit parameters, demonstrating the validity of the theoretical description. The author analysis shows that spin effects have to be taken into account for an understanding of the shapes of the observed interference structures.